Location is not really the key here, but more so the lighting. A picture taken in the gym’s fluorescent lights will look different than your home’s natural lighting. For the truest pictures I have found that you need to position yourself depending on the angle of the light. For wall mounted lighting or natural lighting from a window, you want the camera to be between you and the light. For overhead lighting you want the camera to be in front of the light and your body to be positioned slightly behind the light. The goal is to reduce shadows as much as possible. You also want to try to have as clean a background as possible behind you.
Of course it is optimal to have someone take the pictures for you. I find many people struggle to be able to have someone at their beacon call for this task. In this case I suggest a cam stand for your smart phone and a timer app. If you have decent lighting in a bathroom or kitchen and sufficient room you can often prop your phone on a counter top. You can then flip the viewing screen so you can see what the phone camera will be capturing. Using your cam timer, which you can download for free on the App Store, allow yourself enough to properly position yourself for each pose.
When comparing pictures it does not help to change poses on a weekly basis. It also does not help to only take pictures of strong poses. My suggestion is to utilize 3-4 poses that capture both front, back and side. These would basically be your quarter turns. You can also add in a pose that is a weakness you are trying to bring up as your 4th pose if needed.